I was reading over the forum and people expect zombies to not be released with the trailer and what not, I personally feel, coming with the success from black ops, they will release snippets of it in the trailer. Like literally 1 second things, just to confirm zombies is in the game. Zombies is high up on the list for why people would pre order "black ops 2" early. Possible perks "old black ops maps" on "black ops 2" might be a selling point for hardened editions, or elite sales. If not released in the trailer, I think they may release it on one of the classified things in the next few days.
Also this is super far fetched, and seems like it won't ever happen. But I have always been interested in seeing a co-op zombie related campaign, I think it would be awesome.